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08 / 09Copyleft basics

Copyleft basics

What copyleft licenses require, without the legal lecture

GPL, LGPL, and similar licenses attach conditions to distribution. Here is what teams usually need to operationalize. Not legal advice.

Last updated: July 2, 2026

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Copyleft licenses (GPL, LGPL, AGPL, and similar) attach conditions when you distribute software that includes or links to covered code.

This page explains operational patterns teams encounter. It is not legal advice; counsel interprets how conditions apply to your product.

GPL, LGPL, and AGPL at a glance

The three most common copyleft families differ in when their conditions trigger and how far they reach.

LicenseWhen it appliesWhat it obligates you to do
GPLYou distribute a binary or product that includes GPL codeOffer corresponding source and keep the license text with the product
LGPLYou link to an LGPL library, statically or dynamicallyAllow relinking and provide the library's source and license text
AGPLUsers interact with the software over a network, no shipping neededOffer the source of your modified version to those network users

What teams usually operationalize

  • Identify copyleft components in the shipped inventory, not just direct dependencies.
  • Confirm how components are combined (static link, dynamic link, separate process).
  • Prepare source offer or corresponding source where the license requires it.
  • Include required notice and full license text on the compliance record.
  • Block publish until review gates pass. Do not claim compliance from inventory alone.

Why does copyleft drive enforcement?

Because the conditions are enforceable in court, and rights holders do enforce them: Many public cases involve missed source offers, missing notice, or shipping binaries without the license conditions met. The operational fix is a reviewed record tied to what ships, not a one-time spreadsheet.

Recent rulings show the stakes. Copyleft conditions are treated as enforceable license terms, not optional guidance.

Entr'ouvert v. Orange (France, 2024)

EUR 900,000

Ordered for distributing GPL-licensed code without providing source.

Steck v. AVM (Germany, 2024)

EUR 7,500

An individual developer enforced LGPL obligations and forced the vendor to supply missing installation scripts.

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